This paper, written by researchers from Dalian University of Technology and others, discusses Thermal conductivity enhancement of PEG/SiO2 composite PCM by in situ Cu doping. The paper is published in an important journal < Solar Energy Materials and Solar Cells >. IF：5.018.

In recent years, the research work of microwave chemical instrument used in the synthesis of materials has become a hot direction of scientific research, which has been paid great attention to by many scholars!

In order to improve the energy utilization efficiency during heat charging and discharging processes, Thermal conductivity enhancement of polyethylene glycol (PEG)/SiO2 hybridform-stable phase change material (PCM) was achieved by in situ Cu doping via in situ chemical reduction of CuSO4 through ultrasound-assisted sol–gel process. This method would be an important approach to develop novel hybrid form-stable PCM with high thermal conductivity due to the mild preparation conditions. The XPS result of this material showed that the valence state of copper in PEG6000/SiO2 PCM was mainly zero. The FTIR demonstrated that there was no new chemical bond between Cu, PEG6000 and SiO2. The Thermal properties and thermal stability of the composite PCM were confirmed using DSC and TGA analyses. The phase change enthalpy of Cu/PEG/SiO2 PCM reached up to 110J/g, and the thermal conductivity was 0.414W/(mK) for 2.1wt% Cu in PEG/SiO2, which was enhanced by 38.1% compared to pure PEG. The Cu/PEG/SiO2 hybrid material had excellent thermal stability and good form-stable performance.

Cu/PEG/SiO2 hybrid form-stable PCMs, which exhibit the same phase transition characteristics as PEG, are obtained for latent heat storage applications. In the material, Cu, PEG6000 and SiO2 were physically composite according to the FTIR, and the valence state of copper was mainly zero based on the analytical result of XPS. When Cu is 2.1wt% in PEG/SiO2, the phase change enthalpy and thermal conductivity reached up to 110J/g and 0.414W/ (m K), respectively. The thermal conductivity of the form-stable PCM is increased significantly by in situ doping of Cu particles through in situ reduction of the metal salt solution. The cooling rate tests show that the cooling time is reduced by 69.9% for 2.1 wt% Cu in PEG/SiO2 PCM compared to PEG/SiO2. Thus, problems associated with the low thermal conductivity of PEG/SiO2 and the extra encapsulating PEG are solved. Cu/PEG/SiO2 hybrid form-stable PCMs are synthesized for the first time from chemical methods and are used to improve the thermal conductivities of conventional heat transfer PEG-based PCMs.

Cu/PEG/SiO2 hybrid form-stable PCM was prepared using an ultrasound generator (XH-2008D, Beijing XiangHu Science and Technology Development, PR China).